1. Technical Field
The invention relates to an electrophoretic display, which makes use of movement of charged molecules in an electric field for displaying information, and its manufacturing process.
2. Related Art
Broadly speaking, an electrophoretic display is constituted by an electrophoretic layer provided between a pixel electrode substrate and a common electrode substrate. The electrophoretic layer includes more than one kind of colored electrophoretic particle and a liquid phase disperse medium, which makes the electrophoretic particle movable, and is sealed between the both substrates. And when a pixel signal (voltage) corresponding to two-dimensional image information is applied between each pixel electrode of the pixel electrode substrate and the common electrode substrate, a position of the electrophoretic particle is set corresponding to a level of the pixel signal, whereby an image is formed. As referenced above, the electrophoretic particles move in the disperse medium, while if the electrophoretic display tilts, uneven distribution (unbalanced) of the electrophoretic particles can occur. To prevent this, the electrophoretic layer is divided by partition members or a plurality of electrophoretic particles and the disperse medium are wrapped in a wall member and made into microcapsules. For example, U.S. Pat. No. 5,961,804 shows an example in which the electrophoretic layer of the electrophoretic display is formed by micro-encapsulation.
U.S. Pat. No. 5,961,804 is an example of related art.
In a case where the electrophoretic layer is formed by micro-encapsulation, to form an intricate image, the microcapsules need to be compactly coated all over the substrate without a gap such that a film needs to be made without a gap while microcapsules are tightly in contact with one another.
However, in a currently available technique of forming the electrophoretic layer through the microcapsules, a liquid in which the microcapsules are dispersed is coated on the substrate and dried, thus making it easy to produce gaps among the microcapsules. It is difficult to adjust concentration of the microcapsules in the disperse liquid as well as coating work so as to prevent such phenomenon.
Now, it may be conceived to coat the disperse liquid in advance, so that the electrophoretic layer becomes a thick film in advance, while this is held between two electrode substrates to push the microcapsule layer inside, thereby sticking one microcapsule to another very closely. However, such arrangement causes residual stress (restoring force) to generate inside the microcapsule layer, and exfoliation and deformation tend to occur between the electrophoretic layer and the electrode substrate. In case of a large-sized substrate, overall pressuring (holding) itself is difficult to be applied. Further, if the disperse liquid solidifies, deformation is difficult to occur, hence, before the disperse liquid dries up, the electrode substrates need to be glued together.